The present invention relates to an engine mount used for supporting an automobile engine and the like on a vehicle body.
In general, when an automobile engine and the like is installed on a vehicle body, engine mounts are interposed therebetween in order to control vibration transmission from an engine to a vehicle body. One prior art example of an engine mount is shown in FIG. 3. The engine mount comprises a body side metal fitting 101 fixed to a vehicle body, an engine side metal fitting 102 fixed to an engine, a vibration isolating base body 103 formed of a rubber elastic body interposed between both of the metal fittings 101 and 102, and a liquid chamber 107 partitioned into a main chamber 105 and an auxiliary chamber 106 by a partition member 104, whereby the vibration damping function and the vibration isolating function are achieved by the operation of the vibration isolating base body 103 and a liquid flow effect through an orifice 108 provided at the partition member.
Further, a stopper mechanism 109 is provided in order to prevent a large displacement of the engine mount caused by vibration of an engine and the like. Namely, an outer peripheral flange 110 of the engine side metal fitting 102 is covered by a coating rubber layer 111 so as to form a stopper rubber portion 112. The cylindrical body side metal fitting 101 is provided with a cylindrical portion 113 extending to the engine side so as to oppose the stopper rubber portion 112 and with an inner peripheral flange 114 formed radially inwardly from the cylindrical portion 113. By maintaining a given clearance between both of the above mentioned cylindrical portion 113 and the inner peripheral flange 114 and the stopper rubber portion 112, an excessive displacement of the engine mount, which occurs for example during the vehicle running on a bad road, is absorbed.
In the above stopper mechanism, however, the coating rubber layer of the stopper rubber portion is made of a comparatively soft rubber elastic composition. Accordingly, in case where continuously repeated vibration is exerted on the stopper mechanism during the vehicle running on a bad road for a long period, the stress is likely to concentrate on a boundary portion between the soft coating rubber layer and the outer peripheral flange covered thereby, which results in the occurrence of cracks of the coating rubber layer.
In order to solve the above problem, it may be proposed to enhance the rigidity of the coating rubber layer by increasing a spring constant of the coating rubber layer. However, in view of the fact that the coating rubber layer is formed integrally with the vibration isolating base body, such solution affects the spring constant of the vibration isolating base body, namely, the properties of the engine mount. Alternatively, a different component having a high rigidity may be applied in place of the coating rubber layer. However, such alternate component leads to increasing of material costs and production costs.
In view of the above, it is an object of the present invention to provide an engine mount wherein the durability of the stopper rubber portion is improved without affecting the spring properties of the vibration isolating base body.
It is another object of the present invention to provide an engine mount having a low-cost stopper rubber portion having high durability.
The inventors have made various studies with respect to an engine mount which can improve durability of the stopper rubber portion without affecting the spring properties of the vibration isolating base body and as a result, it has been found that a low-cost stopper rubber portion having a high rigidity can be obtained without affecting the spring properties of the vibration isolating base body provided that a reinforcing metal fitting is embedded in the coating rubber layer to enhance the rigidity thereof.
According to the present invention, a stopper mechanism which absorbs an excessive displacement of an engine mount comprises a cylindrical metal fitting provided at a body side metal fitting surrounding a engine side metal fitting and a stopper rubber portion protruding from the engine side metal fitting so as to oppose to said cylindrical metal fitting. The stopper rubber portion is comprised of an outer peripheral flange protruding radially outwardly from the engine side metal fitting, a coating rubber layer covering said outer peripheral flange, and a reinforcing metal fitting embedded in said coating rubber layer.
Namely, the present invention provides an engine mount having a vibration isolating base body formed of a rubber elastic body interposed between a body side metal fitting and an engine side metal fitting. The body side metal fitting is provided with a cylindrical metal fitting surrounding an engine side metal fitting. The engine side metal fitting is provided with a stopper rubber portion opposed to the cylindrical metal fitting. The stopper rubber portion comprises an outer peripheral flange protruding radially outwardly from the engine side metal fitting, a coating rubber layer covering the outer peripheral flange and a reinforcing metal fitting embedded in the coating rubber layer.
Such reinforcing metal fitting may be embedded in the coating rubber layer in an integral molding process of the coating rubber layer and the vibration isolating base body without taking a separate molding process, and so the production costs bear comparison with the case of manufacturing an engine mount having no such reinforcing metal fitting. The material cost of the reinforcing metal fitting is cheaper as compared with a different component having a high rigidity to be applied in place of the coating rubber layer.
The reinforcing metal fitting may be embedded in any position of the coating rubber layer in order to increase the rigidity of the coating rubber layer. For example, the reinforcing metal fitting may be embedded at a position where vibration is repeatedly received, that is, a position opposed to an inner peripheral face of the cylindrical metal fitting or a position opposed to an inner peripheral flange formed radially inwardly from the cylindrical metal fitting. Preferably, the reinforcing metal fitting is embedded in both of the above mentioned positions, namely, the position opposed to an inner peripheral face of the cylindrical metal fitting and the position opposed to an inner peripheral flange.
Accordingly, the present invention also provides an engine mount comprising a body side metal fitting, an engine side metal fitting and a vibration absorbing base body formed of a rubber elastic body interposed therebetween, a cylindrical metal fitting provided at the body side metal fitting surrounding the engine side metal fitting, an inner peripheral flange extending radially inwardly from the cylindrical metal fitting, a stopper rubber portion protruding from the engine side metal fitting opposed to both the cylindrical metal fitting and the inner peripheral flange, the stopper rubber portion comprises an outer peripheral flange extending radially outwardly from the engine side metal fitting, a coating rubber layer covering the outer peripheral flange and a reinforcing metal fitting embedded in the coating rubber layer, the reinforcing metal fitting being embedded in both a position opposed to the inner peripheral face of the cylindrical metal fitting and a position opposed to the inner peripheral flange respectively.
The reinforcing metal fittings embedded in both positions may be formed as a single unit. Namely, a reinforcing metal fitting may be formed in a L-shape cross section having a radial reinforcing portion opposed to the inner peripheral face of the cylindrical metal fitting and an axial reinforcing portion opposed to the inner peripheral flange. Such reinforcing metal fitting is easily embedded, during a vulcanization-molding process of the coating rubber layer, the comer portion of the L-shape reinforcing metal fitting prevents stress concentration at an outer peripheral edge portion of the outer peripheral flange, so that the rigidity of the stopper rubber portion is well enhanced.
The reinforcing metal fitting is preferred to be disposed in a ring-like configuration all round the stopper rubber portion. Alternatively, however, a reinforcing metal fitting may be disposed only at a position where vibration is repeatedly received, or a plurality of reinforcing metal fittings may be disposed discontinuously all round the stopper rubber portion.
The above mentioned stopper mechanism is applicable to both an engine mount having no liquid chamber and a liquid filled engine mount having a liquid chamber comprising a main liquid chamber and an auxiliary liquid chamber. When applied to a liquid filled engine mount, the functionality and durability of the stopper rubber portion can be improved without affecting the properties of the vibration isolating base body which actuates a filled liquid by piston action.
As mentioned above, in the engine mount in accordance with the present invention, a low-cost stopper rubber portion of high rigidity is obtained by embedding the reinforcing metal fitting in the stopper rubber portion without affecting the properties of the engine mount. Even when continuously repeated vibration is exerted on the stopper mechanism during the vehicle running on a bad road for a long period, no failure occurs on the stopper rubber portion and the durability is improved.